GB2242073A

GB2242073A - Stator coil assembly for electric motors

Info

Publication number: GB2242073A
Application number: GB9001351A
Authority: GB
Inventors: R S Boughton
Original assignee: Smith and Nephew PLC; Watson Marlow Ltd
Current assignee: Smith and Nephew PLC; Watson Marlow Ltd
Priority date: 1990-01-20
Filing date: 1990-01-20
Publication date: 1991-09-18
Also published as: GB9001351D0

Abstract

There is disclosed a stator (1) for an electric motor. The stator includes a number of opposed pairs of stator poles (3, 3'; 4, 4'; 13, 13'; 14, 14'), and a coil is located on each pole. Each coil is located at a different radial distance to that of the two adjacent coils. <IMAGE>

Description

ELECTRIC MOTORS This invention relates to electric motors and more particularly to reluctance motors.

Conventionally, the stator assembly or winding of a reluctance motor comprises a number of electromagnetic coils projecting radially inwards from the stator housing. The stator assembly surrounds a rotor, there being an air gap between the ends of the stator poles and the poles of the rotor.

The design of conventional stator assemblies, makes the provision of the coil windings a laborious and relatively expensive activity. Moreover, conventional design parameters have placed a limitation on the number of stator poles which can be accommodated in a stator housing of a given size. Thus improvements in motor performance have generally had to be accompanied by a concomitant increase in the motor price.

The present invention seeks to overcome the disadvantages of the prior art by the provision of a more compact stator assembly.

Accordingly the present invention provides a stator for an electric motor comprising a housing having a plurality of radially inwardly extending poles each with an associated coil, wherein each coil is located on its pole at a different radial distance to that of an adjacent coil.

The present invention also provides an electric motor comprising a stator and a rotor within the stator wherein the stator comprises a plurality of coil wound stator poles arranged radially around the rotor and wherein each coil is located on its respective pole at a different radial distance to that of an adjacent coil.

In a preferred arrangement, the stator may be constructed with alternating poles of two different lengths. Thus the poles may be closely packed circumferentially around the motor with the associated coils alternately set forward or back from each other.

The inner ends of the poles are suitably each at the same radial distance from the axis of rotation of the rotor.

The invention will be further described and illustrated by reference to the accompanying drawing which is a cross-sectional view of a stator for use in motors of the invention.

The stator 1 comprises a housing 2 from which a number of opposed pairs of projections 3,31, 4,41, 13, 131 and 14, 141 projecting inwardly. The projections define the stator poles and are arranged radially around a rotor (not shown) which is located in the central cylindrical region 20. The stator housing and poles are manufactured from magnetizable materials such as steel.

The poles 3,4 are provided with wire-wound coils 5. The coil may be made from copper wire and may, depending on the required voltage contain for example between 80 and 90 turns.

As will be seen in the drawing each coil is interlocked with respect to the adjacent coil. Thus, for example, in the construction of an eight pole stator the assembly 1, the coils 5 are first located on the pole pieces or limbs 4,41, 14 and 141. A further four coils are then located 3,31, 13 and 131. In the final assembly the coils on limbs 4,41, 14 and 141 are set back with respect to the coils on the alternating poles.

In the manufacture of the stator, the assembly may be made up as a stack of individual lamella stamped out from a thin sheeting of suitable material.

With this arrangement, stators having a greater number of poles, for a given size of motor, can be made than has hereto been possible.

The reluctance motors of the present invention can comprise stators having other than eight poles.

Conventional circuitry may be employed to start and control the motors.

Claims

1. A stator for an electric motor comprising a housing having a plurality of radially inwardly extending poles each with an associated coil, wherein each coil is located on its pole at a different radial distance to that of an adjacent coil.

2. A stator as claimed in claim 1, wherein adjacent coils around the stator are located alternately at first and second radial distances.

3. A stator as claimed in claim 2, constructed with alternating poles of two different lengths.

4. A stator as claimed in any preceding claim, wherein the radially inner ends of the poles are all at the same radial distance from the axis of rotation of the rotor.

5. An electric motor, comprising a stator and a rotor within the stator, wherein the stator comprises a plurality of coil wound stator poles arranged radially around the rotor and wherein each coil is located on its respective pole at a different radial distance to that of an adjacent coil.

6. A motor as claimed in claim 5, wherein adjacent coils around the stator are located alternately at first and second radial distances.

7. A motor as claimed in claim 6, constructed with alternating poles of two different lengths.

8. A motor as claimed in one of claims 5 to 7, wherein the radially inner ends of the poles are all at the same radial distance from the axis of rotation of the rotor.

9. A stator for an electric motor, substantially as herein described with reference to, and as shown in, the accompanying drawing.